characteristics of neutral beam generated by a low angle ... · oklahoma univ. in 2000...

Characteristics of Neutral Beam Generated by a Low Angle Reflection and Its Etch Characteristics by

Halogen-Based Gases

Geun-Young Yeom

SungKyunKwan University

2/32 SKKU

Problems of Current Etch Technology Problems of Current Etch Technology

Scaling down of the device to nano-scale : increased volunability to processing damage

- Physical damage

- Electrical damage (Charging damage)

DRAM Half Pitch Gate Length

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Charging EffectsCharging Effects

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Trend of Etching Tools DevelopmentTrend of Etching Tools Development

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ReseartchReseartch Status of Neutral Beam Etching TechnologiesStatus of Neutral Beam Etching Technologies

1) Gas dynamics or hyperthermal atomic beam (Heating of gas)- Caltech by Giapis in 2000 (laser), PSI Inc. in 2000 (laser),

NEC by Nishiyama in 1995 (thermal heating), etc. Oklahoma Univ. in 2000 (hyperthermal)

2) Ion-neutral scattering (charge exchange process)- Hitach by Mizutani in 1995 (ion removal by retarding grid),

NTT by Matuso in 1995 (ion removal by magnetic field), etc.

3) Ion-electron recombination (surface neutralization)- IBM by Chen in 1997 (sheath recombination by ion and electron)- Tohoku University in 2002 - Ebara Research Co. in 1995 (capillary hole)- Tokyo Univ. in 2000 (focused fast atom beam)

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Neutral Beam Etching using Gas DynamicsNeutral Beam Etching using Gas Dynamics

PSI Inc. in 2000 (laser)

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1) Gas dynamics or hyperthermal atomic beam (Heating of gas)- Caltech by Giapis in 2000 (laser), PSI Inc. in 2000 (laser), - NEC by Nishiyama in 1995 (thermal heating), etc. - Oklahoma Univ. in 2000 (hyperthermal)

2) Ion-neutral scattering (charge exchange process)- Hitach by Mizutani in 1995 (ion removal by retarding grid), - NTT by Matuso in 1995 (ion removal by magnetic field), etc.


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Neutral Beam Etching by Ion Neutral Beam Etching by Ion -- Neutral ScatteringNeutral Scattering

(Tatsumi Mizutani et. al, hitachi, 1995)

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1) Gas dynamics or hyperthermal atomic beam (Heating of gas)- Caltech by Giapis in 2000 (laser), PSI Inc. in 2000 (laser),

NEC by Nishiyama in 1995 (thermal heating), etc. Oklahoma Univ. in 2000 (hyperthermal)

2) Ion-neutral scattering (charge exchange process)- Hitach by Mizutani in 1995 (ion removal by retarding grid),

NTT by Matuso in 1995 (ion removal by magnetic field), etc.


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Neutral beam etching by IonNeutral beam etching by Ion--Electron Recombination (I)Electron Recombination (I)

(Demetre J. Economou et.al, Houston Univ., 2000)

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Recombination by low angle forward scattering

• When the ion beam was reflected by a reflector at the angles lower than 15˚,

most of the ions reflected were neutralized and the lower reflector angle showed

the higher degree of neutralization.

Generation of Directional Neutral Beam Generation of Directional Neutral Beam by Low Angle Reflectionby Low Angle Reflection

5~15 5~15 ˚

5~155~15˚

Reflection plate : Reflection plate : SiSi

Ion gunIon gun

OO22,,SFSF66

90 90 ˚

10~3010~30˚

Neutral beamNeutral beam

Ion beam Ion beam

retarding gridretarding gridreflection platereflection plate

faraday cup or samplefaraday cup or samplerfrf coilcoil

ion beamion beamneutral beamneutral beam

12/32 SKKU

Experimental Low Angle Reflected Neutral Beam SystemExperimental Low Angle Reflected Neutral Beam System

ΦΦ44

RF CoilRF Coil

Deceleration GridDeceleration Grid

Acceleration GridAcceleration Grid

PlatePlate--type Reflectortype Reflector

Neutral Beam FluxNeutral Beam Flux

25 mm25 mm

55oo Reflection AngleReflection Angle

Ion Beam FluxIon Beam Flux

PlasmaPlasma

QuartzQuartz

SubstrateSubstrate

Focusing GridFocusing Grid

ElectromagnetElectromagnet

6 inch6 inch

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0 100 200 300 400 500 600 700

0

100

200

300

400

Ion

curr

ent d

ensi

ty (u

A/c

m2 )

Acceleration voltage (volts)

SF6 SF6 5o reflection

NF3 NF3 5o reflection

CF4 CF4 5o reflection

Ar Ar 5o reflection

Grid hole size:Ø2

Ion Flux and Neutral Flux Ion Flux and Neutral Flux as a function of Acceleration Voltageas a function of Acceleration Voltage

retarding gridretarding grid

reflection platereflection plate

faraday cup or samplefaraday cup or samplerfrf coilcoil

ion beamion beamneutral beamneutral beam

14/32 SKKU

SiOSiO22 Etch Rate as Functions of Acceleration Voltage and Etch Rate as Functions of Acceleration Voltage and Gas Flow Rates for SFGas Flow Rates for SF66, NF, NF33, CF, CF44, and , and ArAr

Condition : reflector angle: 5˚ , rf power: 500WSF6 gas flow rate: 7 sccm

2 4 6 8 10 12 14 16

0

1

2

3

4

5

6

7

8

SiO

2 etc

h ra

te (n

m/m

in.)

Flow rate (sccm)

SF6 NF3 CF4 Ar

100 200 300 400 500 600 700

0

1

2

3

4

SiO

2 etc

h ra

te (

nm/m

in. )

Acceleration voltage (Volts)

SF6 NF3 CF4 Ar

Condition : reflector angle: 5˚ , rf power: 500WVa : 700V

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8 10 12 14 16 18 20 22 24 26100

120

140

160

180

200

Va: 400 VVe: -100 V

Etch

rate

(A/m

in)

Flow rate (seem)

SiO2

8 10 12 14 16 18 20 22 24 26500

600

700

800

900

1000

1100

1200

1300

Va: 400 VVe: -100 V

Etch

rate

(A/m

in)

Flow rate (sccm)

Si

SiOSiO22 and and SiSi Etch Rate as a Function of SFEtch Rate as a Function of SF66 Gas Flow RateGas Flow Rate

Condition : reflector angle: 5˚ , rf power: 400W, distance between reflector and sample : 4 cm, pure SF6, Va: 400 V, Ve: -100 V

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Etch Rate and Etch Selectivity as a Function of Gas Flow Etch Rate and Etch Selectivity as a Function of Gas Flow Rate Using the Neutral Beam Etching SystemRate Using the Neutral Beam Etching System

Condition : rf power: 300W , acceleration voltage: 400V, reflector angle: 5o

reflector material: Si

4 6 8 10 12 14 16 18 200

100

200

300

400

500 Si SiO2 PR

Etc

h ra

te(A

/min

)

CF4 flow rate (sccm)

4 6 8 10 12 14 16 18 20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

Si/PR SiO2/PR

Sele

ctiv

ity

CF4 flow rate (sccm)

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0 10 20 30 40 50 60 700

50

100

150

200

250

300

350

400

450

Si SiO2 PR

Etc

h ra

te(A

/min

)

H2/(H2+CF4)%

0 10 20 30 40 50 60 700.0

0.5

1.0

1.5

2.0

2.5

3.0

H2/(H2+CF4)%

Si/PR SiO2/PR

Etc

h se

lect

ivity

Etch Rate and Etch Selectivity as a Function of HEtch Rate and Etch Selectivity as a Function of H22 to CFto CF44

Using Neutral Beam Etching SystemUsing Neutral Beam Etching System

Condition : rf power: 300W , CF4+H2: 15sccm, acceleration voltage: 400V, reflector material: metal, reflector angle: 5o

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SEM Micrograph of SiOSEM Micrograph of SiO22 Etch ProfilesEtch Profiles(Neutral Beam Etching)(Neutral Beam Etching)

Condition : SF6 2.5 sccm, rf power: 400 W , acceleration voltage: 400V, reflector angle: 5o

etch mask : Cr

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Condition : CF4 15sccm, rf power: 300W , acceleration voltage: 400V, reflector material: metal,

reflector angle: 5o

SEM Micrograph of SEM Micrograph of SiSi Etch ProfilesEtch Profiles

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0

100

200

300

400

500

0

30

60

90

120

150

180

210

240

270

300

330

0

100

200

300

400

500Incident beam direction

SiO

2 etc

h de

pth(

A)

Reflected azimuthal angle φr (o)

Incident ion energy: 400V

10o

5o

-100 -80 -60 -40 -20 0 20 40 60 80 100

0

100

200

300

400

500

Reflected azimuthal angle φr (o)

Incident ion energy: 400V

10o

5o

SiO

2 etc

h de

pth(

A)

0 20 40 60 80 100

0

100

200

300

400

500

600

5o

10o

15o

20o

SiO

2 etc

h de

pth(

A)

Reflected polar angle θr (o)

0

100

200

300

400

500

600

0

20

40

60

80100

120

140

160

1800

100

200

300

400

500

600

Reflected polar angle θr (o)S

iO2 e

tch

dept

h(A

)

5o

10o

15o

20o

Condition : SF6 10 sccm(0.6 mTorr), rf power: 400W , acceleration voltage: 400Vreflector material: Si

Effect of Reflector Angle on Reflected Angle and Flux Effect of Reflector Angle on Reflected Angle and Flux of the Neutralsof the Neutrals

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0100200300400500600700

0

20

40

60

80100

120

140

160

1800

100200300400500600700

SF6+

SiO2 DLC Si Metal


Effect of Reflector Materials on Reflected Angle and Effect of Reflector Materials on Reflected Angle and FluxFlux

Condition : SF6 10 sccm(0.6 mTorr), rf power: 400W , acceleration voltage: 400Vreflector angle: 5o

0 20 40 60 80 100

0

100

200

300

400

500

600

700

DLC Si Metal SiO2

SiO

2 etc

h de

pth(

A)

Incident angle θi: 5o


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CC--V Characteristics V Characteristics Before and After Neutral Beam & ICP Etch Before and After Neutral Beam & ICP Etch

-6 -5 -4 -3 -2 -1 00.00E+000

2.00E-011

4.00E-011

6.00E-011

8.00E-011

1.00E-010

1.20E-010

Cap

acita

nce

(F)

Voltage (V)

reference neutral 30 min ICP 2 min

-6 -5 -4 -3 -2 -1 0

1.00E-011

2.00E-011

3.00E-011

4.00E-011

5.00E-011

Cap

acita

nce

(F)

Voltage (V)

reference neutral 30 min ICP 2 min

<middle dot: 200um x200um><Big dot: 300um x 300 um >

Al(5000A)

Si3N4(50nm)SiO2(2nm)

Si p-type, (100)10Ωcm

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II--V Characteristics V Characteristics Before and After Neutral Beam & ICP EtchBefore and After Neutral Beam & ICP Etch

<Big dot: 300um x 300 um >

<small dot: 100um x 100um>

<middle dot: 200um x200um>

0 -2 -4 -6 -8 -100.0

1.0x10-7

2.0x10-7

3.0x10-7

4.0x10-7

5.0x10-7

Voltage (V)

Cur

rent

(A)

reference neutral beam etching ICP etching

0 -2 -4 -6 -8 -100.0

1.0x10-7

2.0x10-7

3.0x10-7

4.0x10-7

5.0x10-7

Voltage (V)

Cur

rent

(A)


Treatment

- ICP plasma

power: 500 W, bias voltage: -100 V,

gas: O2, time: 2 min

- Neutral beam

power: 500 W, acceleration voltage: 400V,

extraction voltage: -100V

gas: O2 , time: 30 min, distance: 5 cm0 -2 -4 -6 -8 -10

0.0

1.0x10-7

2.0x10-7

3.0x10-7

4.0x10-7

5.0x10-7

Voltage (V)

Cur

rent

(A)


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SEM Micrograph of PolySEM Micrograph of Poly--SiSi and Polyand Poly--Si/SiOSi/SiO22 Etch Profiles (ICP Etch Profiles (ICP Etching) Etching)

(Poly-Si) (Poly-Si/SiO2)

condition : rf power: 700W, Bias voltage: -75V pure SF6 5 mTorr,

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SEM Micrograph of PolySEM Micrograph of Poly--SiSi and Polyand Poly--Si/SiOSi/SiO22 Etch Profiles (Ion Etch Profiles (Ion Beam Etching)Beam Etching)


condition : SF6 2.5 sccm(0.3 mTorr), rf power: 400W ,Ve: -100V, Va: 400V, etch mask: Cr

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SEM Micrograph of polySEM Micrograph of poly--SiSi and SiOand SiO22 Etch ProfilesEtch Profiles(Neutral Beam Etching)(Neutral Beam Etching)


condition : reflector angle: 5˚, SF6 2.5 sccm(0.3 mTorr), rf power: 400W , Ve: -100V, Va: 400V

27/32 SKKU

GaNGaN and and GaAsGaAs Etching Etching as a Function of Flow rate, Additive Gasas a Function of Flow rate, Additive Gas

Process conditions

Fixed power : 400W, Fixed acceleration voltage : 400V

<Cl2+Ar Flow rate>Total flow rate : 15sccm

<Cl2 Flow rate>

0 5 10 15 20

10

15

20

25

30

35

Etc

h ra

te (A

ngst

rom

)

Cl2 flow rate (sccm)

GaAsGaN

0 5 10 15

20

25

30

35

40

45

Etc

h ra

te (A

ngst

rom

)

Ar flow rate (sccm)

GaAsGaN

28/32 SKKU

Damage Analysis Etched Damage Analysis Etched nn--GaNGaN, , GaAsGaAs

Process conditionsFixed acceleration voltage : 400V, pure Cl2, Gas flow rate : 3sccm,

350 400 450 500 550 600 650

1

10

100

PL In

tens

ity (a

.u.)

Wavelength (nm)

As-received ICP treatment Neutral treatment

<GaN PL> <GaAs PRS>

1.30 1.35 1.40 1.45 1.50 1.55 1.60

Room Temp.

Reference ICP ethcing Neutral etching

∆R

/R (a

rb. u

nits

)

Photon energy (eV)

GaAs PhotoReflectranceGaN Photoluminescence

29/32 SKKU

II--V Characteristics of V Characteristics of GaNGaN LEDsLEDs after Neutral after Neutral Beam Etching of Beam Etching of pp--GaNGaN

-10 -5 0 5

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

1

10

100

Log

A (m

A)

Voltage (V)

Reference ICP etching Neutral beam etching

-15 -10 -5 0 5

0

20

40

60

80

100

Cur

rent

(mA

)

Voltage (V)

Reference ICP etching Neutral beam etching

Condition- Neutral beam etching : Power 400W / Bias +400V / CF4 15sccm / 40min / thickness 600-650Å- ICP etching : Power 400W / Bias -400V / CF4 15sccm / 15sec / thickness 750-800Å

Multi quantum welln - contact : Ti/Al

n - GaN

p - GaN

p - contact : ITOp - contact : Cr/Au

Hole size : 2μm

Device Structure

P-GaN surfaceReference

Neutral beam etch

ICP etch

30/32 SKKU

GaNGaN Device Efficiency Device Efficiency after Neutral Beam Etching of after Neutral Beam Etching of pp--GaNGaN

<Reference (No pattern)><Neutral beam etch (patterned)>

420 440 460 480 500 5200

200

400

600

800

1000

1200

Emis

sion

inte

nsity

(A.U

)

Wave length (nm)

Reference Neutral beam textured

Emission at 20mAEmission intensities were increased about 22%in neutral beam textured GaN LED (OES analysis)

Hole patterns

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Commercialization Commercialization Alpha Version Alpha Version –– for 12inch for 12inch DiaDia. Silicon . Silicon NanoNano ProcessingProcessing

Item 사양

Ion source

- Source type : ICP

- Power 3000W

- Density : 5.5E+11(4mTorr, 2500W)

Grid

&

Reflector

Plasma+++ +

+

Wafer

+ bias

Control voltage

Ground

Grid

Reflector Plasma++++++ ++

++

Wafer

+ bias

Control voltage

Ground

Grid

Reflector

- Grid에 DC Bias 인가

- Grid hole size; 2, 3, 4mm

- Grid gap; 2, 4, 6mm

- Reflector angle; 3, 5, 7°

- Chuck & reflector gap; 50, 100, 150mm

- Grid material : Graphite

Chuck

- Tilting(Manual, 45°) & Rotating(Automatic, 15RPM)

- Lift pin & Mechanical clamp

- No Cooling & heating

Chamber

&

Vacuum system

- Vertical type

- Chamber pressure : 0.3mTorr with Ar 40sccm

- TMP 4200ℓ/s

- Gate valve : ø400, Step motor Operation(Pressure control)

Gas- Gas box type : IGS(1.25)

- Gas line : 14 line

<설비 구성> <설비 사양>

RF Matcher

Plasma source

Grid & Reflector

Chuck

Process Chamber

Pump

Control box

32/32 SKKU

Summary

Using a low energy reflection of reactive ion beam, directional reactive neutral beam for chargeless etching was successfully fabricated.

By using the neutral beam, nanoscale etching of silicon and silicon oxide could be achieved.No charging damage was detected by the use of the neutral beam while the conventional ICP etching showed a significant damage such as leakage of gate oxide, RIE-lag, etc.

It is believed that, neutral beam etching technique is benificial for the nanodevice processing not only for the top-down devices but also for the bottom-up devices

characteristics of neutral beam generated by a low angle ... · oklahoma univ. in 2000...

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